Typical water cooled and moderated nuclear reactor plants for power generation comprise a large pressure vessel containing cooling and neutron moderating water, and have a heat generating core of fissionable fuel submerged a substantial distance beneath the surface of the cooling and moderating water. The submerged fissionable fuel of the core must be periodically replaced, including the removal of spent fuel and replacement with new fuel, as well as rearranging partially spent fuel within the core. Due to the high levels of radioactivity within the nuclear reactor pressure vessel, the means for handling the water submerged fuel must be remotely controlled by an operator from out beyond the water containing reactor pressure vessel.
Conventional fuel handling systems comprise a fuel handling mast or pole extending down from above an open top of the water containing reactor pressure vessel with a grapple head affixed to the lower end of the mast. The system is designed for attachment to fuel bundles and their transfer while submerged in the reactor vessel to remove spent fuel and introduce new fuel, and rearrange fuel bundles within the core. The fuel handling mast is frequently supported on and operated from a movable platform which can travel back and forth over an open top of the water containing reactor vessel above the fuel core. Typically the fuel handling mast is mechanically telescoping downward from the supporting movable platform to facilitate reciprocal travel of the grapple head affixed to the lower end of the mast down into and back up from the interior of the reactor vessel. This arrangement provides greater versatility for transferring fuel bundles within and about the reactor vessel.
To facilitate operating personnel in manipulating such fuel handling systems with the grappling devices submerged a substantial depth below the surface of the water containing reactor vessel from a safe position above the open top of the reactor vessel, underwater viewing means are commonly employed. For example, underwater periscopes or television cameras suspended on a pole and connected to an above surface monitoring screen have been utilized for enabling remotely located operators to more accurately and clearly observe their underwater manipulation and relative location of the grappling head on the mast with respect to fuel assemblies to be transferred, and its application to fuel bundles.
However, controlling the manipulation of two distinct underwater units and their coordination by a remotely located operator is cumbersome and slow, and space limitations sometimes impede positioning of such underwater viewing mechanisms in conjunction with the fuel handling means.
Fuel bundles for typical water cooled and moderated nuclear reactor plants used to generate power commonly consist of a multiplicity of small diameter sealed tubes elements enclosing fissionable fuel which are grouped, spaced apart, into an assembled unit. Each assembled unit of the grouped tube elements is provided with an upper and lower end piece having sockets to receive and secure the end portions of the grouped tube elements, and the overall assembled unit is substantially surrounded with an open ended housing or channel unit. A handle or bail is provided on the upper end piece of the assembled units for convenient and effective graphing and secure attachment of a transferring means such as a grapple device. The identification number of each assembled unit or fuel bundle is stamped on the top of its bail.
The grouping of a multiplicity of the fuel containing tube elements in assembled units greatly facilitates the transfer of fuel in reloading operations, among other benefits.